Repeat proteins are formed by repetition of modular units of protein sub-structures. The overall structural architecture of repeat proteins is dictated by the internal geometry of the protein and the local packing of the repeat building blocks. These features are generated by underlying patterns of amino acid sequences, that themselves, are repetitive in nature.
Naturally existing repeat proteins play important biological roles as macromolecular binding and scaffolding domains, enzymes, and building blocks for the assembly of fibrous materials. The structure and identity of these repeat proteins are highly diverse, ranging from extended, super-helical folds that bind peptide, DNA, and RNA partners, to closed and compact conformations with internal cavities suitable for small molecule binding and catalysis.